public final static boolean isValidEmail(CharSequence target) {

  if (TextUtils.isEmpty(target)) {

    return false;

  } else {

    return android.util.Patterns.EMAIL_ADDRESS.matcher(target).matches();

  }

}

val EMAIL_ADDRESS_PATTERN: Pattern = Pattern.compile(

    "[a-zA-Z0-9\\+\\.\\_\\%\\-\\+]{1,256}" +

            "\\@" +

            "[a-zA-Z0-9][a-zA-Z0-9\\-]{0,64}" +

            "(" +

            "\\." +

            "[a-zA-Z0-9][a-zA-Z0-9\\-]{0,25}" +

            ")+"

)

​

fun String.isValidEmail(): Boolean {

    return EMAIL_ADDRESS_PATTERN.matcher(this).matches()

}

(?:[a-z0-9!#$%&'*+/=?^_`{|}~-]+(?:\.[a-z0-9!#$%&'*+/=?^_`{|}~-]+)*|"(?:[\x01-\x08\x0b\x0c\x0e-\x1f\x21\x23-\x5b\x5d-\x7f]|\\[\x01-\x09\x0b\x0c\x0e-\x7f])*")@(?:(?:[a-z0-9](?:[a-z0-9-]*[a-z0-9])?\.)+[a-z0-9](?:[a-z0-9-]*[a-z0-9])?|\[(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?|[a-z0-9-]*[a-z0-9]:(?:[\x01-\x08\x0b\x0c\x0e-\x1f\x21-\x5a\x53-\x7f]|\\[\x01-\x09\x0b\x0c\x0e-\x7f])+)\])